29.11.2010 21:12, Ann W. Harrison wrote:

> Postgres, InnoDB (the MySQL transactional engine), and Oracle
> implement another isolation mode between "Snapshot" and
> "Read Committed." Normal Select statement works just as
> they do in Firebird's Snapshot mode. Update, delete,
> and select for update wait if there's a newer version of
> the record than the transaction can see, then succeed when
> the transaction that created the newer version commits.

Can't say about PG and MySQL, but Oracle doesn't just wait till commit, but in most
cases also restart the statement after that. IMHO, it is quite unpleasant process,
overcomplicated and AFAIK, Oracle has some bugs in this place.

--
SY, SD.